650 Rider > > xs650 > > Motorcycle Systems > > Fuel > > MPG

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

What is your MPG - and is it mostly City - Highway or a mix?

ine is 35-40 mpg - city driving.

I have an 81 with 34's:
135 MJ - 135 Airjets
45 idle jets
John's needles - Canadian jets.

Runs GREAT!
Plugs Look Normal.

Good Pickup
But my milage seems low.

Even Stock I only got about 45 mpg city.

Cooltouch · Posted: May 9, 2008, 1:13 pm Post subject: Re: MPG

Mine's about the same as yours -- high 30s usually. By now, most gas stations around these parts should no longer be selling the winter gasoline formulations. I'm hopeful that the mileage improves somewhat.

Best,

ichael

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

I think i get about the same with same set up on an 80. 135 main, stock air, bored out pilot and johns kits. I live in suburbs so it is some hwy and some town driving i weigh about 200lbs.I havent checked the mileage lately due to weather. i want to do it a few times normal driving and a few time driving in a gas conserving maner and see what i come up with.
I am using bp7s for plugs

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Yes - one thing I forgot to mention to john, was that I weigh about 200 pounds - that will have an impact.

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

Last year with a stock engine and a stretched out timing chain (retarded cam timing) I was getting 60 MPG. Had it apart to fix the trans and replaced the cam chain it dropped to 55 MPG. This year with it bored to 700 cc, 10:1 compression, mildest Megacycle cam, cleaned up ports and rephased crank I'm getting 50 MPG. This is with some highway, some paved back roads and a little in town riding.

It would be nice to still be getting 60 but I wouldn't want to trade off the power. Cool

tacoswild · Posted: May 9, 2008, 8:06 pm Post subject: Re: MPG

I was getting 44 with stock gearing and jetting on my 71. I dropped a couple teeth on the rear sprocket and went up one on the main jet size last time I worked on it, don't know if it changed yet.

weekendrider · Posted: May 9, 2008, 9:59 pm Post subject: Re: MPG

I get 46-48.
Stock 79 Standard.
Running the original jetting, gearing, points, coil, etc. etc.
Ride like I stole it sometimes. Mostly just ride.
I do let the stale old air out and pump new in every spring to prevent tire rot. And try to change oil every 1K.

xs1961 · Posted: May 10, 2008, 7:26 am Post subject: Re: MPG

40-60 here on 18/29 gearing stock carbs Smile

25-45 with 34mm roundslides Surprised

killer · Posted: May 10, 2008, 9:51 am Post subject: Re: MPG

'79 with neutronics ignition, stock carbs, somewhat loud exhaust, 17/32 sprockets.
45-55 mpg

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

I was getting mid 40s around town, about 50 highway on my '78 with 17/32 gearing, stock carbs slightly modded (one up on the mains), K&N pods, MAC headpipes, and Commando mufflers.

I just completed the single points conversion with a hotter Accel coil and swapped on a 33T rear sprocket. For the mostly local and back road riding I do, this size seems better. It really didn't alter my speed/RPM ratio much. Before, 4K gave me 65, now about 63 MPH. I'm hoping the better burn from the hot coil will offset the slightly lower gearing and MPGs won't change much.

pumps · Posted: May 10, 2008, 2:05 pm Post subject: Re: MPG

MPG? Who cares? That's just some BS story I give my wife that "I'm saving gas honey" when she complains about the bikes taking up garage space!

Really I think it's 40 something but haven't really cared enough to check closer.

xsleo · Posted: May 10, 2008, 5:58 pm Post subject: Re: MPG

my 75 gets about 65 on a long slow cruise, 50-55 mph. push it up to 70 - 75 mph it drops to 45. try to stay outta town. to many idiots in town.

Buzz · Full Member Joined: Jun 27, 2005 Posts: 37

Before I changed the carbs on my 82 Heritage to the VM34's I was getting 51 mpg after the change 41. A lot of response, but 10mpg less.

Buzz

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

For most of what I can tell - I dropped about 5mpg when I went from stock 42.5 idle jets to 45's from Mikes.

Runs good -

Why do I care?

Because I have no gas gauge - and a 2.5 gallon tank - I use my odometer as a gas gauge....

That and for tuning reasons....

xsjohn · Posted: May 12, 2008, 3:17 pm Post subject: Re: MPG

Problem with big pilots is if you set them to far out you will loose gas mileage fast.........if you hear a heavy bass report from the pipes when taking off they are probaboy set to far out....and decelshould be somewhat quiet.....since gas went up with my 46 pilots I turn them in till it won't idol properly....."""each side independently"""then nudge them out till it runs good to be sure they aren't to far out and wasting gas......and each side should be treated independently because there may not work the same with the same turns.........xsjohn

And the catch 22 is .....stay off the throttle........

mcaiki · Posted: June 2, 2008, 12:45 am Post subject: Re: MPG

Right now I'm averaging 36-37 on my 75. Hopefully I'll have that boosted a little bit soon.

Seems that even with getting better mileage than the car, I tend to take the long way wherever I am headed and burn extra gas anyway. Shame it costs so much these days, but I'm still going to burn a tank now and then just for the sake of the ride!

xsjohn · Posted: June 2, 2008, 1:12 am Post subject: Re: MPG

Working with a fellow member we found that position 4 on the 4N8 jet needle was not necessary and that moving the clip to position three did not hurt performance and boosted mileage ...........some testing there and watching the plugs should help mileage ......... 36-37 miles to the gallon could easily wash the rings .........xsjohn

mcaiki · Posted: June 2, 2008, 8:59 am Post subject: Re: MPG

xsjohn - are you saying that too much gas will damage the rings? Would it cause too much pressure or wash the lubrication away? I don't mean to hijack the thread, but now you have me curious.

The plugs look good at higher throttle, but foul badly at the lower end. Also, when cruising below 3000 rpms it is inconsistent - a little jumpy/sputtery. When I'm cruising at 3500-4000 rpms it runs fine.

xsjohn · Posted: June 2, 2008, 9:22 am Post subject: Re: MPG

Too much fuel will reduce the lubrication on the rings and kill gas mileage and performance.....Some very qualified members have been testing the older 38 carbs with my custom needles and we did find that the recommended 4th needle position is probably too rich on those 74-75 carbs hurting gas mileage........could try putting the clip in the center position and she how she goes....and watch the plugs for any signs of leaness.......jayel has been working on getting the mixtures straightened out on the 74-75's with some good results I might add.........xsjohn

jopower · Posted: June 3, 2008, 4:08 am Post subject: Re: MPG

I get ~55 mpg on my '78 SE. My altitude is ~5000 ft. (this does make a diff!) It has 140 mains (up 2) and stock pilots, meter rods down 1 as the low end was rich. The airbox covers have large windows cut in them for 5x the intake area from stock. Sprockets are 18 front and 34 rear (I heard that increasing front size reduced chain wear and the rear has to go up 2 to match). I have just put in 35kv 5 ohm coils, allowing a .035 spark gap, and will report back on changes.

For those getting low mpg, sounds like your fuel system needs a clean out. I do it every Spring. I'd also bet there are a few petcocks leaking out there. Do you come out to the bike and smell gas? Look for soggy filters and the dark spot under the bike that isn't oil and burns merrily.

Fuel system clean-out: You'll need typical tools, carb cleaner, Liquid Wrench w/teflon, spray silicon, good fuel and perhaps compressed air, Marvel Mystery Oil and Form-a-gasket (I like Grey). An old cupcake pan and cheap reading glasses are real handy.

Start at the tank and petcocks. Off with the tank! All last year's old fuel goes to the car or lawn mower. Is the cap seal OK? Spray with silicon if good, replace if not. Remove petcock(s) and clean tank of any debris or rust. The petcocks have filters sticking up out of them; clean if necessary. There are 2 sides to each petcock I've seen. Carefully disassemble each separately, noting orientation of parts. Inspect for damaged rubber, replace as necessary. Spray good/new rubber parts with silicon and rub in. Reassemble and rotation of selectors should be smooth. Put the petcocks back on the tank (only use sealer for the tank seal) and put a gallon in. Check for leaks in "on" and "reserve" positions. "Prime" should drain fast.

Remove air filters or air boxes (depending on length of your fingers) for easy access to carb throats. Remove carb float bowls with a #2 Phillip's w/2-3" shaft. There are hints in the bottom of each as to possible troubles (rust, gunk, tiny bits, etc). Carb spray everything and clear gunk from all passages. The choke circuit is suspect so pay attention to it. If it leaks, you'll run rich. Spray carb slides (in throats) afterward with Liquid Wrench and check with finger for smooth operation up and down. Do the same for the butterfly shafts and linkages.

The floats and needle valve are next. A small rod holds them in. If you have one, put a small pan under the carb and push/pull the pin out while holding the floats (needle nose help). Slowly drop the floats and needle into your pan or hand. Inspect for damage as you would any set. Clean, repair or replace as necessary.

Next the large (~1/4" diam) fuel pickup tube should be removed from each carb (ignore the little thin one, except to spray it clear). It has several pin point holes running down the side. Work it out of the bottom of the carb, pulling straight down. There is an "O" ring at the top of the tube. Inspect for damage or looseness in the carb (i.e.: easy to remove tube from carb). If it leaks you'll never get the carb to run quite right. If it's loose it can drop a bit into the bowl. Replace the "O" ring if indicated (note it's a very specific size and a bit tough to put on). The first time inserted, a newly "O" ringed fuel tube will be a bit tough to seat in the carb base. The fuel tube's little holes must be clear. Rod each with a small pin, thin wire or staple, or spray to clear. If even one is closed the mixture can go off.

With the fuel tube out, the metering rod can be seen hanging down. It should be clean and move up and down with carb slide. Usually you won't need to remove it. (If it came off with the float bowl or tube, that's a rare problem.) A decent manual (Yamaha or Clymer's) will talk about installing and adjusting it. Spray the fuel tube with Liquid Wrench and work back into the carb (remember the rod is inside it when in place).

With the bowls off and fuel tank in place, turn petcock to "prime" for a few seconds (put a cup under carb). There should be a satisfying flow that flushes the lines. Reinstall floats and needle valve. Check float drop and adjust to spec. Install float bowl after checking bowl gasket. Prime carbs and run her up. Unless the bike is misadjusted, I'll bet you notice a considerable improvement in response or function.

If not, I'd then check the vacuum diphrams at the top of the carbs for cracks and sags. Is the diphram return spring still good? Is the vacuum vent to the carb throat clear? Before spending bucks elsewhere, find out.

And the Marvel Mystery Oil? An excellent top-end lublicant, just one ounce in (most) every tank keeps the fuel parts lubed, tank (almost) rustless, valves, valve stems, plugs and combustion chambers clean and pipes grey inside. And the most important tank is the 1st of the season if you layup over Winter. Use 2-4 ounces in that one, depending on tank size.

BIG HINT: the best thing I've ever done is replace the little Phillips float bowl screws with stainless Allen screws (30 cents each at Ace Hardware). They are SOOOO much easier to replace on the tip of an Allen wrench. In fact, where ever possible I've replaced the Phillip's with Allen's on my bike. No more strips or fumbles and the stainless looks cool and doesn't rust!

Good riding and rubber side down! Smile

nj1639 · Posted: June 5, 2008, 6:08 am Post subject: Re: MPG

133 miles till it hit reserve on last fill-up. Stock 'cept for 17/33 gearing, 2 into 1 exhaust and John's needles. Mixed hills, hollers, highway and town drivimg.
Not sure how much is left in the tank when you hit reserve.

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

How much do these special tanks hold ? I was figuring about 3 gallons. I think the other ones hold 3.9.?

xsjohn · Posted: June 5, 2008, 8:02 am Post subject: Re: MPG

nj1639.....sounds like you are getting decent mileage......50+....did you leave the stock main jet in there......those ole BS34 carbs do pretty good don't they when spanked a bit ............xsjohn

nj1639 · Posted: June 5, 2008, 12:11 pm Post subject: Re: MPG

Hey John,
Yep, stock mains, I'm pleased.
Rick

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